Picture retrieval system, and record carrier and device for use in the system

ABSTRACT

A picture retrieval system is which comprises a record carrier (184) and a read device (11). A coded picture (8 TV, 16 TV, 64 TV, 256 TV) composed of consecutive coded picture lines is recorded in a continuous track (20) of the record carrier (184). The read device scans the track to read coded picture lines recorded in the track and moves the read head (280) to a track portion having a selected address with a certain search accuracy. Together with the coded picture lines (APDB) a line number (LN) and a line synchronization are recorded in the track (20). The line number specifies the sequence number of the relevant picture line in the coded picture. The line synchronization specifies the beginning of the relevant picture line. Moreover, addresses (ADLN#1, . . . , ADLN#1009) for a number of coded picture lines of the coded picture are recorded in a portion (IIDB) of the track, to specify the positions where the relevant picture lines have been recorded in the track (20). The device also searches a coded picture line on the basis of the addresses read from the track portion (IIDB).

This is a continuation of application Ser. No. 07/856,214, filed asPCT/NL91/00174, Sep. 18, 1991 now abandoned.

FIELD OF THE INVENTION

The invention is related to the field of image processing of recordedvideo such as displaying enlarged representations of a selected portionof a recorded picture.

BACKGROUND OF THE INVENTION

The invention relates to a picture retrieval system comprising a recordcarrier and a read device, a coded picture composed of consecutive codedpicture lines being recorded in a contiguous track of the recordcarrier, which track has been provided with addresses, the read devicecomprising a read head for reading the recorded coded picture lines byscanning the track, means for moving the read head with a specificsearch accuracy to a track portion having a selected address.

The invention further relates to a record carrier and a read device foruse in the system.

Such a system, such a record carrier, and such a read device are known,inter alia from the book "Compact Disc Interactive, a designer'soverview", published by Kluwer (ISBN 9020121219). This book describes aso-called CD-I system which enables coded pictures to be recorded on aCompact Disc. Representations of the recorded coded pictures can bereproduced by means of a CD-I player.

SUMMARY OF THE INVENTION

For specific picture processing operations, such as for exampledisplaying enlarged representations of a selected part of the codedpicture the recorded coded pictures have to be read out only partly. Asthe overall read-out time of a coded picture may be long for codedhigh-resolution pictures it desirable that coded picture lines can beretrieved selectively.

It is an object of the invention to provide means enabling thoseportions of the track in which a selected coded picture line has beenrecorded to be rapidly retrieved.

According to the invention this object is achieved in that together withthe coded picture lines, a line synchronization code and a respectiveline number are recorded on the record carrier at the beginning of eachcoded picture line. Each line number specifies the sequence number ofthe relevant coded picture line in the coded picture, and each linesynchronization code marks the location of the beginning of the relevantcoded picture line, Addresses for a number of coded picture lines of thecoded picture are also recorded on the record carrier, which addressesspecify where the relevant picture lines have been recorded in thetrack. The read device reads the records carrier and comprises means forselecting a coded picture line within a selected coded picture, meansfor reading the recorded addresses of the picture lines of the selectedpicture, means for selecting on the basis of the addresses thus read anaddress for a track portion situated before the track portion where therecording of the selected coded picture line begins, and means forcausing the read head to be moved to the track portion specified by theselected address, and means for subsequently detecting the read-out ofthe beginning of the selected coded picture line on the basis of theread-out line numbers and line synchronization code.

By adding a line synchronization code and line number to every codedpicture line in the picture file and by recording addresses of a numberof coded picture lines it is possible to rapidly find an address of atrack portion situated at a short distance before the beginning of therecording of the desired coded picture line. The system in accordancewith the invention is particularly advantageous if a variable-lengthcoding has been selected for coding the picture. The track spacerequired for the storage of a coded picture line then varies frompicture line to picture line. Indeed, in that case the track positionwhere the recording of a specific coded picture line begins can nolonger be derived unambiguously from the starting position of therecording of the first coded picture line.

Moreover, the addition of the line synchronization code and the linenumber have the advantage that in the case of an incorrect read-out theerror propagation can be limited to at the most the length of one codedpicture line. This is because at the beginning of every picture line theline number is known and the starting point of the coded line is known,so that the decoding and reproduction of the incorrectly read picturelines can be restored simply.

An embodiment of the system is characterized in that the lengths of thetrack portions situated between the positions specified by the recordedaddresses of the coded picture lines substantially correspond to thesearch accuracy.

If during the displacement of the read head this head is moved to theportion with the address specifying a coded picture line preceding theselected coded picture line it becomes highly probable that after thedisplacement of the read head this head has reached a position situatedbefore the position where the recording of the desired coded pictureline begins. In this way it is avoided that after the displacement ofthe read head another displacement of the read head in the oppositedirection is necessary. The waiting time from the instant at which theread-head displacement has ended till the instant at which the selectedcoded picture line is reached is limited, thereby enabling a shortoverall access time to be obtained. Moreover, the amount of track spaceneeded for recording the addresses of the number of picture lines isminimal.

A further embodiment of the system is characterized in that the track isa spiral track, the means for moving the read head being adapted to movethe read head in a direction transverse to the tracks, the lengths ofthe track portions situated between the positions specified by therecorded addresses of coded picture lines substantially corresponding tohalf the length of a turn of the spiral track.

This embodiment makes optimum use of the fact that the search accuracyin the case that a read head is used which is radially moved over thespiral track is equal to plus or minus half the length of a turn of thespiral track.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail, by way of example,with reference to FIGS. 1 to 31, in which

FIGS. 1a, 1b and 1c show a picture-storage system, a picture retrievaland reproduction system, and a simplified picture retrieval andreproduction system respectively,

FIG. 2 shows a suitable format for recording picture information on arecord carrier,

FIG. 3 illustrates a suitable coding of picture information,

FIG. 4 illustrates a suitable residual coding to be used for in thecoding of picture information,

FIG. 5 illustrates a suitable arrangement of the color information of apicture for a series of coded pictures of increasing resolutions,

FIG. 6 shows a format of a subfile containing a residually codedpicture,

FIG. 7 shows a record carrier on which recorded coded picture lines havebeen arranged in a suitable manner,

FIG. 8 shows a picture composed of picture lines,

FIG. 9 illustrates a number of different picture processing functions,

FIG. 10 shows an embodiment of a retrieval and reproduction systemcapable of displaying picture information in accordance withpreferential reproduction settings,

FIG. 11 shows a suitable format for recording preferential reproductionsettings on the record carrier,

FIG. 12 shows a suitable format for storing preferential reproductionsettings in a non-volatile memory,

FIG. 13 shows a mosaic picture composed of sixteen low-resolutionimages,

FIG. 14 shows in greater detail an embodiment of the simplified pictureretrieval and reproduction system,

FIG. 15 shows an embodiment in which control data groups can be arrangedin packets,

FIG. 16 shows a data extraction circuit for use in the picture retrievaland reproduction system shown in FIG. 14,

FIG. 17 shows in greater detail an embodiment of the picture storagesystem,

FIG. 18 shows a recording unit for use in the picture storage system,

FIG. 19 diagrammatically illustrates the CD-ROM XA format,

FIG. 20 shows a suitable organisation of the record carrier if thepicture information has been recorded in accordance with a CD-I format,

FIGS. 21, 23 and 24 show suitable configurations of picture lines ofabsolutely coded pictures for a number of different resolutions if therecorded information has been divided into blocks in accordance with aCD-I format,

FIG. 22 shows a picture made up of picture lines to illustrate theconfiguration shown in FIG. 21,

FIG. 25 shows an example of a picture processing unit,

FIGS. 26 and 27 illustrate picture processing functions to be performedby the picture processing unit,

FIG. 28 shows an embodiment of a read device,

FIGS. 29 and 31 diagrammatically show examples of a simplified pictureprocessing unit, and

FIG. 30 illustrates the operation of the simplified picture processingunit shown in FIGS. 29 and 31.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

FIG. 1a shows a picture storage system 12 in which the invention can beused. The picture storage system 12 comprises a picture scanning unit 1for scanning pictures on a picture carrier 3, for example a strip-shapedphotographic negative or slide. The picture scanning device 1 furthercomprises a picture coding unit for coding the picture informationobtained upon scanning. The coded picture information is recorded on arecord carrier 184 by means of a recording unit 5 under control of acontrol unit 4. Prior to recording the control unit 4 can apply anoptional picture processing, for example to enhance, correct or edit thepicture representation defined by the coded picture information. Forthis purpose the control unit may comprise picture processing meanswhich are known per se. The recording unit 5 may comprise, for example,an optical, a magnetic or a magneto-optical recording device. In view ofthe high storage capacity of optical and magneto-optical record carriersit is preferred to use an optical or a magneto-optical recording device.The control unit 4 may comprise a computer system, for example aso-called "personal computer" or a so-called work station with suitablehardware and application software.

FIG. 1b shows a picture retrieval and reproduction system for retrievingand displaying representations of coded pictures stored on the recordcarrier 184 by means of the picture storage system 12. The pictureretrieval and reproduction system 13 comprises a read unit 6 forlocating and reading out selected coded pictures under control of acontrol unit 7. Representations of coded pictures thus read can bedisplayed on a picture display unit. Such a picture display unit maycomprise a display screen 8, which for example forms part of the controlunit 7, or an electronic image printer 9 for generating a hard copy 15of a representation of the read-out coded picture. The picture retrievaland reproduction system 13 may further comprise an additional recordingdevice 5a, by means of which the coded picture information read by meansof the read device 6, after an optional picture processing operationperformed by the control unit 7 for the purpose of enhancement,correction or editing. The control unit in the picture retrieval andreproduction system 13 may comprise a computer system, for example a"Personal Computer", or a work station with suitable hardware andapplication software. Although such a system is very suitable for thecontrol task to be performed and the optional picture processing it hasthe drawback that it is comparatively expensive.

In general, it is desirable to have such an expensive computer systemfor the control unit in conjunction with the electronic image printer 9because of the complexity of the control and picture processingfunctions. However, if it is merely desired to display selected codedpictures on a display screen, the computing capacity and storagecapacity of a computer system in the form of a personal computer or workstation are high in comparison with the control functions to beperformed. In that case it is preferred to employ a simplified controlunit with a limited computing and storage capacity and a limited dataprocessing speed.

FIG. 1c shows such a simplified picture retrieval and reproductionsystem 14. This simplified system 14 comprises a display unit 10 and apicture retrieval and read unit 11 comprising the read unit 6. A controlunit for controlling the retrieval and read operation and, ifapplicable, a limited picture processing can be accommodated in one ofthe units 10 and 11, but suitably in the unit 11. When the control unitis accommodated in the retrieval and read unit 11 it is possible toemploy, among others, a standard TV set or monitor unit for the picturedisplay device.

This is an advantage, in particular for consumer uses because theconsumer then merely has to purchase the retrieval and read device todisplay the representations of the pictures.

As a result of their comparatively high cost the picture storage system12 shown in FIG. 1a and the picture retrieval and reproduction system 13shown in FIG. 1b are particularly suitable for central uses, for examplein photoprocessing laboratories.

For recording coded picture information it is preferred to record theinformation on the record carrier in a predetermined format and order.FIG. 2 shows a suitable format and order, in which files containingcoded picture information bear the references IP1, . . . , IPn.Hereinafter the files IP1, . . . ,IPn will be referred to as picturefiles. Moreover, a plurality of control files BB have been recorded.These files contain control data which is used for controlling theread-out of the coded picture information, for the purpose of performingoptional picture processing operations on the picture information readand for the purpose of displaying representations of the coded pictureinformation. It is to be noted that part of the control data may beincluded in the picture files. Preferably, this part of the control datais the part relating specifically to the control of the read-out,display and picture processing of the coded picture informationcontained in the relevant picture file. The advantage of this is thatthe required control data becomes available at the instant at which itis needed, i.e. at the instant at which the picture file is read.

Apart from the picture files Ip and the associated control files BB itmay be desirable in a number of cases to record files with additionalinformation, for example audio information or text information. Suchaudio and/or text information may relate to, for example, coded pictureinformation and can then be reproduced or displayed when therepresentations of the relevant coded picture information are displayed.The files with additional information are referenced ADD and may berecorded, for example, after the coded picture information.

For every picture stored the picture files contain a plurality ofsubfiles, which each define a representation of the same scannedpicture, the resolutions of the representations defined by these codedpictures being different. In FIG. 2 the different subfiles for thepicture file IP1 bear the references TV/4, TV, 4TV, 16TV, 64TV, 256TV.The subfile TV defines a representation of the scanned picture with aresolution corresponding substantially to a standard NTSC or PAL TVpicture. Such a picture may comprise, for example, 512 lines of 768pixels each. The subfile TV/4 represents the scanned picture with aresolution which in the horizontal and the vertical direction has beenreduced linearly by a factor of 2 relative to the resolution of thepicture represented by the subfile TV. The subfiles 4TV, 16TV, 64TV and256TV define picture representations whose horizontal and verticalresolution has been increased linearly by a factor of 2, 4, 8 and 16respectively. Preferably, the subfiles are arranged in such a way thatthe resolutions of the representations defined by the successive codedpictures increase (linearly) in steps of 2. During reproduction, whenthe consecutive subfiles are generally read successively, it is thensimple to first display a representation of a picture of low resolutionand, subsequently, to replace this representation wholly or partly byrepresentations of the same picture of each time increasing resolution.This has the advantage that the waiting time before a picturerepresentation appears on the display screen is minimized. Indeed, onaccount of the limited amount of information needed for this, theread-out time of a coded picture defining a low-resolutionrepresentation is short in comparison with the read-out time of encodedpictures defining higher-resolution representations.

A generally known representation of pictures is that in which thepicture is composed of a matrix of small areas of constant luminancevalue and/or constant color value. In this representation it iscustomary to select the areas of constant color value to be larger thanthe areas of constant luminance value.

An area of constant color value will be referred to hereinafter as acolor pixel and an area of constant luminance value will be referred tohereinafter as a luminance pixel. A row of color pixels of a width equalto the full picture width will be referred to hereinafter as a colorpicture line. A row of luminance pixels of a width equal to the fullpicture width will be referred to hereinafter as a luminance pictureline. A picture represented by luminance picture lines and color picturelines can be defined simply by a coded picture by assigning to eachluminance pixel and color pixel a digital code specifying the relevantluminance value and color values.

FIG. 3 by way of illustration shows the structure of a picture of colorpixels and luminance pixels. The luminance pixels bear the referencesigns (Y₁,1 ; . . . ; Y_(K),R). The color pixels bear the referencesigns (C₂,1 ; . . . ; C_(K-1),R-1). It is to be noted that in FIG. 3, asis customary, the dimensions of the color pixels in the horizontal andthe vertical direction is twice as large as the dimensions of theluminance pixels. This means that the resolution of the colorinformation in the horizontal and the vertical direction is a factor oftwo lower than the resolution of the luminance information.

A suitable picture coding is that in which a digital code or digitalcodes is/are assigned to every luminance pixel and every color pixel,the code(s) defining the absolute value of the luminance component Y andthe absolute values of the colour-difference components U and Vrespectively. Such a coding will be referred to hereinafter as anabsolute picture coding. Preferably, representations of a number oflow-resolution pictures are recorded as absolutely coded pictures. Thisenables the picture information to be recovered in a simple manner. Thisis particularly advantageous for the simplified picture retrieval andreproduction system 14, because this enables the price of such a system,which is intended for the consumer market, to be kept low by the use ofsimple picture decoding systems.

The use of a picture file with a number of absolutely coded pictures ofdifferent resolutions simplifies the reproduction of representations ofcomposite pictures, where a representation of a small low-resolutionpicture is displayed within the outline of a representation of ahigher-resolution picture. The reproduction of such a representation ofa composite picture is referred to as "Picture in Picture" (or "PIP").Moreover, recording a plurality of absolutely coded pictures definingrepresentations of the same picture with different resolutionssimplifies the reproduction of enlarged representations of details of acoded picture. Such a function is also referred to as the TELE-function(or ZOOM-function). The availability of absolutely coded pictures withdifferent resolutions implies that for some of the TELE functions andPIP functions the required picture information is directly available andneed not be derived by means of additional picture processing operationsto be performed by complex circuits.

In the recording of picture information it is customary to record thecoded pixels in rows (or lines) or sometimes in columns. Recording inlines is to be preferred because in the customarily used picture displayunits the picture information should be presented in the form of lines.

When the absolutely coded pictures are recorded in the subfiles TV/16,TV/4 and TV it is preferred not to record consecutive coded picturelines contiguously. Such method of arranging the recorded information isfrequently referred to as "interleaving". The advantage of such a methodis that if a comparatively great part of the information cannot beretrieved owing to defects of the disc or other causes, it reduces thelikelihood that two adjacent picture lines in the representation of thecoded picture are reproduced incorrectly. Representations with faults inadjacent picture lines are comparatively difficult to restore. This isnot the case with representations in which erroneously read pixels (or apicture line) are situated between two correctly read picture lines. Inthat case the erroneously read pixels (or picture line) can be replacedsimply by pixels (or a picture line) derived from one or both adjacentpicture lines. It is to be noted that erroneously read pixels can alsobe restored readily by the use of so-called error-correction codes. Thecorrection of errors on the basis of such error-correction codes iscomparatively intricate and is therefore less suitable for use in thesimplified picture retrieval and reproduction system 14, in which theuse of complex circuits should be avoided whenever possible in view ofthe resulting high cost.

In the case that the picture information is recorded on a disc-shapedrecord carrier with a spiral track the part of the track needed forrecording a coded picture will occupy a plurality of turns of the spiraltrack. In view of a simple restoration of erroneously read picture linesit is then desirable that the coded picture lines defining adjacentpicture lines in the representation of the picture to be reproduced donot adjoin each other, neither in the track direction (also referred toas tangential direction) nor in a direction transverse to the track(also referred to as radial direction), which will be explained withreference to FIGS. 7 and 8.

FIG. 7 shows a disc-shaped record carrier 70 on which picture 80composed of consecutive picture lines l1, . . . , ln has been recordedin a spiral track 71 in the form of a series of absolutely coded picturelines BLa1, BLa3, BLa5, BLa7, BLa9, BLa11, BLa13, BLa2, BLa4, . . . Theabsolutely coded picture lines BLa1, . . . , BLa13 represent the picturelines 11, . . . , 13 respectively. The absolutely coded picture lineshave been recorded in such a way that the information of consecutivepicture lines is not contiguous either in a radial or in a tangentialdirection. The reference numeral 72 refers to an unreadable discportion, also called disc defect. The defect shown extends over morethan one turn of the spiral track 71. Since the coded picture linesdefining adjacent picture lines of the representation do not adjoin oneanother either radially or tangentially this prevents coded picturelines which define adjacent picture lines in the representation frombeing read incorrectly as result of the occurrence of disc defects. Itis to be noted that for the sake of clarity the length occupied by thecoded picture lines BLa on the recording is shown to be substantiallygreater than in reality. In practice, it occurs comparatively often thata disc defect occupies the space which will be covered by a plurality ofconsecutively recorded coded picture lines. In view of the requirementthat adjacent picture lines should not be defined by adjacently recordedcoded picture lines the order of the absolutely coded picture lines inthe track depends strongly on the length of the turns of the spiraltrack and on the length required for recording an absolutely codedpicture line. Arrangements suitable for recording absolutely codedpicture lines will be described in more detail further on in thedescription.

For high resolutions the storage of absolutely coded picture informationhas the drawback that the amount of information to be recorded is verylarge. For such high-resolution pictures a residual coding is verysuitable. In such a residual coding differences between the signal valueof the pixels of the high-resolution picture and the signal value of thecorresponding part of the lower-resolution picture are determined andsubsequently encoded.

To illustrate this coding method FIG. 4 shows one luminance pixel Y of alow-resolution picture and four luminance pixels Y₁,1 '; Y₂,1 '; Y₁,2 'and Y₂,2 ' of the corresponding higher-resolution picture in the casethat the horizontal and the vertical resolution is increased by a factorof 2. Instead of the absolute luminance value of the luminance pixelsY₁,1 ', . . . , Y₂,2 ' the residual coding encodes differences(hereinafter referred to as residual values) between the luminancevalues of the luminance pixels Y₁,1 ', . . . , Y₂,2 ' and the luminancepixel Y. In this way the residual values of a complete picture can bedetermined both for the luminance and for the color information. As thenumber of residual values equal to zero or being very small is large incomparison with the number of large residual values a substantial datacompression can be obtained by applying an additional coding in whichthe residual values are non-linearly quantized and are subsequentlysubjected to, for example, a Huffman coding.

A residually coded picture can be used as a basis for a new residualcoding for a picture with further increased resolutions. Thus, byrecording one absolutely coded low-resolution picture and a series ofresidually coded pictures of increasing resolutions in compressed formit is possible to record a plurality of coded pictures definingrepresentations of the same picture with increasing resolutions. In thepicture file IP1 shown in FIG. 2 the pictures in the subfiles TV/4 andTV are absolutely coded and the pictures in the subfiles 4TV, 16TV, 64TVand 256TV are residually coded, with non-linear quantization and Huffmancoding. Such a coded picture will be briefly referred to hereinafter asa residually coded picture.

The color information is also coded residually in a way similar to theluminance information. However, the horizontal and the verticalresolution of the consecutive residually coded color informationincreases by a factor of four instead of by a factor of two as with theluminance information. This means that a picture file containing onlyresidually coded luminance information and no color information (4TV and64TV) alternates with a picture file containing both residually codedluminance information and residually coded color information (16TV and256TV), see FIG. 2. Leaving out the color information in the subfiles4TV and 64TV reduces the required storage capacity and the access timeto the coded picture information in the picture file. However, theabsence of the color information in the subfiles 4TV and 64TV need notadversely affect the picture quality during reproduction. This isbecause during the reproduction of a representation of a coded picturefor which no color information has been recorded the color informationof the next coded picture defining a representation of higher resolutionor the color information of the preceding coded picture defining arepresentation of lower resolution can be utilised. In order to reducethe total access time to the required picture information it is to bepreferred to record the color information U, V in the subfiles 16TV and256TV contiguously to the luminance information Y in the subfiles 4TVand 64TV, as is illustrated for the file IP* in FIG. 2. An even shorteraccess time to the required high-resolution color information isobtained if the color information in the subfiles 16TV and 256TV isdivided into a portion U*, V* and a portion U', V', the portion U*, V*defining color information having a horizontal and vertical resolutionwhich is twice as low as the resolution represented by U*, V* and U', V'together. This is possible, for example, in that for a picture the codedcolor information of one of the four available pixels of the picture isfirst recorded in U*, V* and subsequently the coded color information ofthe other pixels of the picture is recorded, as is illustrated in FIG.5. In this Figure the color pixels belonging to U*, V* (UV11; UV31;UV51; . . . ) are represented as shaded blocks and the color pixelsbelonging to U', V' (UV21; UV41, . . . , UV12; UV22; UV2) arerepresented as non-shaded blocks. The information U*, V* in 16TV and256TV defines the color information with a horizontal and verticalresolution which is half the resolution of the luminance informationdefined by the subfiles 4TV and 64TV respectively. Thus, the luminanceinformation in the subfile 4TV and 64TV respectively together with thecolor information U*, V* in the subfiles 16Tv and 256TV respectivelyagain define a representation whose horizontal and vertical resolutionof the color information is equal to half the resolution of theluminance information. This means that the ratio between the resolutionof the color information and the luminance information of arepresentation defined by the combination of the luminance informationof a subfile 4TV and 64TV and the color information U* V* of a subfile16TV and 256TV respectively is equal to the ratio between the resolutionof the color information and the luminance information of therepresentations defined by the subfiles TV/4, TV, 16TV and 256TV as atotal, so that representations of all the stored coded pictures with thesame resolution ratio between color and luminance information can bedisplayed.

However, it is to be noted that during the reproduction of therepresentation of the coded picture recorded by means of the subfile 4TVit is also possible to use the color information of the subfile TV orthe complete color information of the subfile 16TV.

As already stated, it is customary to record the coded pixels line byline.

When the residual coding described above is used, using a non-linearquantization and Huffman coding, the residual values are represented bymeans of codes of varying length. This means that the space required forrecording the residually coded picture lines is variable. Therefore, theposition at which the beginning of the residually coded picture line isrecorded is not unambiguously defined by the beginning of recording ofthe first coded picture line of a coded picture. This complicates theselective read-out of the coded picture lines, for example only thosecoded picture lines needed to carry out a TELE function. This problemcan be mitigated by recording a line number LN and line synchronizationcode LD (see FIG. 6) at the beginning of each coded picture line BL andline synchronization code LD. The line synchronization code may be, forexample, a unique bit combination which does not occur within the seriesof Huffman codes representing information of the residually codedpicture elements. It is to be noted that the addition of the linesynchronization codes LD and line numbers LN has the additionaladvantage that it facilitates the read synchronization and significantlyreduces error propagation after an erroneously read residual code.

A very fast retrieval of selected coded picture lines can be achieved inthat the addresses at which the recordings of coded picture lines on therecord carrier begin are recorded on the record carrier in a separatecontrol file, preferably at the beginning of each subfile. In FIG. 6these addresses have been indicated, by way of example, as ADLN#1, . . ., ADLN#1009 in the control file IIDB at the beginning of the subfile4TV. The picture line information in the form of the series ofresidually coded picture lines is inserted in the section APDB of thesubfile 4TV. (The section APDB represents the actual picture informationwithin the subfile 4TV).

Generally, when searching for the starting points of the picture lineson the record carrier during a coarse search process a read element ismoved relative to the record carrier to a position at a short distancebefore the starting point where the recording of the coded picture linebegins. Subsequently, a fine search process is carried out in which,while the record carrier is scanned with a speed corresponding to thenormal read speed, the beginning of the recording of the selectedresidually coded picture line is awaited, after which reading of theselected coded picture line is started. The accuracy with which the readelement can be positioned relative to the record carrier during thecoarse search process is limited and in optical data storage systems itis generally much greater than the distances between the positions atwhich the recordings of successive coded picture lines on the recordcarrier begin. Therefore, it is preferred to store only the startaddresses of a limited number of coded picture lines whose startingpoints of recording are spaced apart by a distance substantially equalto the accuracy with which the read element can be positioned during acoarse search process. This enables the information of selected codedpicture lines within a stored coded picture to be located and readrapidly without an unnecessarily large amount of space being needed forthe storage of address data. In the case of a disc-shaped record carrierthe average search accuracy during a coarse search process, in which theread element is radially moved over the disc, is by definition equal tohalf the length of one turn of the disc, which means that the distancesbetween the positions specified by addresses substantially correspond tohalf the length of one turn of the disc when disc-shaped record carriersare used.

Reproduction Settings

The stored coded pictures generally define a number of pictures inlandscape format (i.e. for a faithful reproduction the picture should bedisplayed in an orientation in which the width of the picture is largerthan the height of the picture) and a number of pictures in portraitformat (i.e. for a faithful reproduction the picture should be displayedin an orientation in which the height of the picture is larger than thewidth of the picture).

By way of illustration FIG. 1 shows an image carrier with some picturesin landscape format (2a, 2b, 2c and 2d) and one picture in portraitformat (2e). On the record carrier all the coded pictures are recordedas though they were representations of pictures in landscape format.This is in order to enable a uniform picture scanning to be used withoutthe necessity to detect whether the scanned picture is of the landscapeor portrait type and to change over the scanning and/or pictureprocessing depending upon the detection result. However, this means thatduring reproduction the representations of portrait format pictures willbe displayed in an incorrect rotated position. This can be precluded byproviding a possibility to assign a rotation code to the recorded codedpictures, which code indicates whether the representation should berotated during reproduction and, if this is the case, whether therepresentation should be rotated through an angle of 90, 180 or 270degrees. This rotation code can be included in every picture file IP1, .. . , Ipn. It is also possible to record these rotation codes in thecontrol file BB or to store these rotation codes in a non-volatilememory arranged in the read unit or connected to this unit.

During reproduction it is then possible to determine on the basis of therotation code whether the representation to be displayed should berotated and, if this is the case, a rotation through the desired anglecan be performed prior to reproduction. A drawback of including therotation codes in the picture files IP is that these rotation codes haveto be determined already during scanning of the pictures. In practicethis means that an operator of the picture storage system shoulddetermine for each scanned picture whether the stored picture is to berotated during reproduction, because the known auxiliary devices are notalways capable of detecting whether a scanned picture is of landscape orportrait format and whether the picture is presented to the scanningunit with the correct orientation. This is undesirable in particularbecause it implies that an operator must be present during recording,which makes it difficult to realise a fully automated picture storagesystem 12.

If the rotation codes are already available during recording of thecoded picture information it will be advantageous to record these codeson the record carrier. In the case of the file organisation shown inFIG. 2 a suitable position for recording the rotation codes is thesubfile FPS of the control file BB. For reasons of user convenience itis desirable to specify, apart from the required rotation, whetherinstead of a representation of stored coded pictures a representationwhich is slightly shifted (to the left, right, top or bottom) should bedisplayed. This is certainly desirable if the display area within whichthe representation is to be displayed in a display unit is smaller thanthe dimensions of the representations, because it is possible that animportant detail of the picture falls outside the display area. Thedesired shift can be specified by assigning a translation code to everycoded picture. In FIG. 9 a suitable translation coding for a picture 90is defined by means of the coordinates xp and yp of a vertex 91 of thepicture 91 to be displayed after translation. By means of a translationcode and a magnification code it is possible to specify themagnification factor with which a certain part of the original pictureis to be displayed. The reference numeral 93 indicates an enlargedrepresentation of a part of the picture 90, defined by a translation xp,yp and a magnification factor of 2. In addition to the above data it isalso possible to include other picture display data in the subfile FPSof the control file BB, such as for example parameters specifying acolor or luminance adaptation to be applied before a representation ofthe coded picture is displayed. Moreover, it is advantageous to storethe desired sequence in which the pictures must be reproduced in thesubfile FPS within the control file BB.

The afore-mentioned information about the display sequence, rotation,translation, magnification, brightness and color adaptations and otherpicture processing operations to be performed prior to reproduction ofthe representation of the coded picture will be referred to hereinafteras preferential reproduction settings. A collection of preferentialreproduction settings defining the preferred sequence as well as all thedesired picture processing operations for all the coded pictures on arecord carrier will be referred to hereinafter as a set of preferentialreproduction settings. It may be advantageous to record more than oneset of preferential reproduction settings in the file FPS. This enablesa different display sequence and other picture processing operations tobe selected by different persons, for example persons within a family.It also allows a user to make a choice from different sets ofpreferential reproduction settings.

It is to be noted that when a record carrier of the write-once type isused the sets of preferential reproduction settings can be recorded onthe record carrier only if they are available during recording. Thisrequires human intervention during recording. During reading of therecord carrier a set of preferential reproduction settings is selectedand the representations of the coded pictures can be displayed inconformity with the selected set of preferential reproduction settings.

FIG. 10 is a block diagram of an embodiment of a picture retrieval anddisplay system by means of which representations of coded pictures canbe displayed in conformity with a selected set of preferentialreproduction settings. In this diagram the reference numeral 100 refersto a read unit for reading the record carrier. For the purpose ofapplying the information being read the read unit 100 is coupled to acontrol and signal processing unit 101. From the information receivedfrom the read device 100 the unit 101 selects the file FPS containingthe set(s) of preferential reproduction setting(s) and stores this(these) set(s) in a control memory 102. By means of a data entry unit103, for example a remote control device, a user can select a set fromthe control memory 102 and can subsequently activate the unit 101 tostart the read cycle, in which the coded picture information is read inthe sequence specified by the selected set of preferential reproductionsettings under control of the unit 101. After the coded pictureinformation has been read out this information is processed inaccordance with the selected set of preferential reproduction settingsand is applied to a display unit 104.

It may occur that after some time the preferential reproduction settingsstored on the record carrier are no longer entirely in compliance withthe user's wishes or that no or wrong preferential reproduction settingshave been recorded on the record carrier. This can cause a problem, inparticular if the record carrier is of a type which cannot beoverwritten, because the recorded preferential reproduction settingsthen cannot be adapted. This problem can be mitigated by providing theretrieval and display system in FIG. 10 with a non-volatile memory 105in which together with a record carrier identification code a new set ofpreferential reproduction settings or information about the desiredchanges of the preferential reproduction settings relative to the set ofpreferential reproduction settings recorded on the record carrier isstored for the record carrier specified by means of the record carrieridentification code. In view of the limited storage capacity of thenon-volatile memory 105 it is desirable to record the informationnecessary for the preferential reproduction settings in a most compactform, for which reason it is preferred to record the information aboutthe changes of the preferential reproduction settings.

FIG. 11 shows by way of example a suitable format 110 of thepreferential reproduction settings included in the file FPS on therecord carrier. The format 110 comprises a section DID in which theunique record carrier identification code is stored. Such a code maycomprise a large random number generated by means of a random-numbergenerator and recorded on the record carrier. The code may comprise atime code indicating the time in years, months, days, hours, minutes,seconds and fractions of seconds. Alternatively, the record carrieridentification code may comprise a combination of a time code and arandom number. In the format 110 the section DID is followed by sectionsFPS1, FPS2, . . . , FPSn in which a number of different sets ofpreferential reproduction settings are stored. Each of the preferentialreproduction setting sections FPS1, . . . , FPSn contains a portion SELin which a set identification number for each of the different sets ofpreferential reproduction settings to be selected by different users arespecified, and a portion specifying the sequence SEQ in which therepresentations of the stored pictures are to be reproduced. Thisportion is followed by the coded sections FIM#1, . . . , FIM#n storingfor the pictures 1, . . . , n preferential processing operations to beperformed before the representation of the relevant picture aredisplayed.

FIG. 12 shows by way of example a suitable format 120 in which theinformation about the desired adaptations of the set of preferentialreproduction settings can be stored in the non-volatile memory 105. Theformat 120 comprises a section 121 specifying combinations of recordcarrier identifications and set identification numbers for whichinformation about preferential reproduction settings has been stored. Toeach of these combinations a pointer is assigned, which pointer isincluded in the section DID-POINT and specifies the address of thesections DFPS1, . . . , DFPSn in the non-volatile memory 105.

Every section DFPS comprises a portion LSEQ with a code indicating thespace (for example in numbers of bytes) required to specify the newsequence. If the portion LSEQ indicates a length not equal to zero LSEQwill be followed by a portion NSEQ with the data specifying the newdisplay sequence. After NSEQ the new preferential processing operationsare specified for every picture with modified preferential processingoperations. ROT indicates the section with the rotation code. Thesections LTELE and LPAN specify the length available for the storage ofthe new data relating to picture magnification (in a section NTELE) andpicture translation (in a section NPAN). In this way it is possible toselect the accuracy with which the picture processing information is tobe stored. Thus, it is possible, for example, to define three differentlengths indicating three different accuracies. LTELE and LPAN arefollowed by the portions NTELE and NPAN. If the information about thepicture magnification and picture translation need not be changed thisis indicated by the length zero in LTELE and LPAN. By storing only thepreferential processing operations for pictures with modifiedpreferential processing operations the space required for the storage ofthe new preferential reproduction setting is reduced considerably. Apartfrom the reduction of the required storage space by said recording ofthe differences it is possible to obtain an additional reduction byspecifying the length required for the storage of modified data. Whenthe record carrier is read an adapted set of preferential reproductionsettings is derived from the preferential reproduction settings recordedon the record carrier and the differences stored in the memory 105, andthis adapted set is stored in the memory 102.

Instead of, or in addition to, the non-volatile memory 105 a changeablememory 106, for example in the form of a magnetic card, EPROM, EEPROM orNVRAM, can be employed for the storage of preferential reproductionsettings in the retrieval and display system shown in FIG. 10.

This has the advantage that a user can display the picture informationon a record carrier in accordance with the same preferentialreproduction setting on different picture retrieval and display systemsto which a changeable memory 106 can be connected. When one of the twoor both memories 105 and 106 are used for the storage of preferentialreproduction settings it is desirable that a selection is made from thedifferent sets of preferential reproduction settings defined by the setsof preferential reproduction settings on the record carrier and by themodifications of the preferential reproduction settings stored in thememories 105 and 106. For this purpose the unit 101 should compriseselection means. These selection means may be of a type which areoperated by the user to make a choice from the various sets ofpreferential reproduction settings defined for one specific recordcarrier and selection number by the preferential reproduction settinginformation stored on the record carrier and in the memories 105 and106. However, alternatively these selection means may be of a typewhich, prior to reproduction on the basis of the contents of thememories 105 and 106 and the sets of preferential reproduction settingsrecorded on the record carrier, determine the sets of preferentialreproduction settings available for the relevant record carriers andstore them, for example, in the memory 102. Subsequently, one of theavailable sets of preferential reproduction settings in the memory 102is selected in accordance with a predetermined selection criterion.Preferably, the selection criterion is such that the highest priority isassigned to the preferential reproduction setting information in thechangeable memory 106, medium priority to the preferential reproductionsetting information in the non-volatile memory, and the lowest priorityto the preferential reproduction settings on the record carrier. If theunit 101 comprises a computer, automatic selection can be realised byloading the computer with a suitable selection program.

Now reference is made again to the file OV in FIG. 2, which for all thepicture files IP1, . . . , IPn comprises a subfile TV/16 containing anabsolutely coded low-resolution picture. Recording a file OV has theadvantage that an overview of the coded picture information recorded onthe record carrier can be obtained with a minimal access time. This ispossible, for example, by successively by displaying the coded picturesin the subfile TV/16 as representations which wholly or partly fill thedisplay screen, preferably in the sequence defined by the selected setof preferential reproduction settings. However, it is also possible tocompose a representation in the form of a so-called mosaic picture fromthe subfiles, in which mosaic picture a large number of representationsof the coded low-resolution pictures contained in the subfiles TV/16 arearranged in the form of a matrix, preferably in an order dictated by theselected set of preferential reproduction settings. By way ofillustration FIG. 13 shows a mosaic picture 130 made up of therepresentations (IM#1, IM#3, . . . , IM#26) of sixteen low-resolutionsubfile pictures.

SIMPLIFIED RETRIEVAL/REPRODUCTION SYSTEM

FIG. 14 shows an embodiment of the picture retrieval and display systemof FIG. 1c in more detail. In the present system the picture retrievaland read unit 11 comprises the read unit 6, a control unit 140 and apicture processing unit 141. The read unit 6 supplies the informationread from the record carrier to the control unit 140 and to the pictureprocessing unit 141 via a signal path 142. The control unit 140 thenselects specific information contained in the control files BB and IIDBfrom the information read. The picture processing unit 141 selectspicture information from the information read and converts this pictureinformation into a form suitable for the display unit 10. The read unit6 and the picture processing unit 141 are controlled by the control unit140 on the basis of the data entered by a user, for example via a dataentry unit 143, and on the basis of the control data in the controlfiles BB and IIDB.

In view of the large amount of information for every recorded picture itis preferred to read files containing picture information with a highspeed, i.e. with a high bit rate, in order to minimize the read time perpicture read. However, this means that the data in the control file isalso read with a high bit rate. The control task is performed by thecontrol unit 140. This control task requires only a limited dataprocessing rate, enabling a simple slow low-cost microcomputer having alow data processing rate to be used for this purpose. However, ingeneral such a low-cost microcomputer is not capable of processing thecontrol data which is supplied at a high rate during read-out of thecontrol files BB and IIDB. This is because the rate at which the controldata is presented (which rate is substantially equal to the pictureinformation rate) is too high to enable it to be processed by the slowlow-cost computer. This problem can be mitigated in that every bit groupcontaining control data is recorded n times (n being an integer greaterthan or equal to 2) in succession on the record carrier. A group of ntimes repeatedly recorded bit groups will be referred to hereinafter asa packet. Packets of n identical bit groups are then supplied when thecontrol data is read. FIG. 15 by way of example illustrates the mannerin which the control data in the control files BB and IIDB can besupplied by the read unit 6 in the case that n is equal to 2 and thenumber of bits per bit group is 8.

In FIG. 15 the bit groups bear the reference numeral 150 and the packetsbear the reference numeral 151. The number of bits per bit group iseight and the number of bit groups per packet is two.

By repeating identical bit groups n times it is achieved that the rateat which the control data is supplied by the read unit is reduced by afactor of n without the use of additional auxiliary functions. By asuitable choice of the value of n it is thus possible to reduce the rateat which the control data is applied to the slow microcomputer system ofthe control unit 141 to such an extent that it can be handled by theslow microcomputer system 144. Between the signal path 145 and themicrocomputer system 144 a data extraction circuit 145 can be arrangedto supply each of the packets 151 of control data to the microcomputersystem 144 as one bit group at a rate equal to the bit group repetitionrate divided by n.

Such a data extraction circuit 145 may comprise, for example, a register160 (see FIG. 16a) which is loaded with a clock frequency equal to thebit group repetition rate divided by n. This clock signal can beobtained very simply by using one bit within each bit group 150 as asynchronization bit 152. To the synchronization bits 152 of successivebit groups 150 a logic value may be assigned which alternates with afrequency related to the repetition rate of the packets 151 of bitgroups 150. The alternation frequency may be equal to half therepetition rate of the packets (as shown in FIG. 15) or a multiplethereof. This has the advantage that a clock signal can be used which isderived directly from the synchronization bits.

The data extraction circuit 145 comprises a clock extraction circuit 161which supplies an alternating clock signal corresponding to thealternating logic values of the synchronization bits to a load controlinput of the register 160. The register 160 is of a customary type whichis loaded with a bit group of each packet 151 under control of the clocksignal. The clock extraction circuit 161 also transfers the clock signalto the microcomputer system 144 via the signal line 162. Preferably, thebit groups in the control file are arranged in so-called frames, whichbear the reference numeral 154 in FIG. 15. In that case it is desirablethat the beginning of each frame 154 can be detected simply. A verysimple detection can be achieved by inserting at the beginning of theframes 154 a plurality of frame synchronization groups 153 withsynchronization bits 152 which exhibit a predetermined pattern of logicvalues 150 which differs distinctly from the possible patterns of logicvalues of the synchronization bits 152 which can occur in the otherpackets.

Each frame 154 has a portion 155 containing redundant information forthe purpose of detecting whether the frame has been read-in correctly bythe microcomputer 144. An incorrect read-in may be caused, for example,by a program interrupt, in which the process of reading in the controldata is interrupted in order to carry out another control program. Sucha control program can be called, for example as a result of the input ofdata in the data entry unit 143, in order to fetch the entered data fromthe data entry unit 143. Since an incorrect read-in of data from thecontrol files BB and IIDB is generally caused by a program interrupt,this requires that the error correction performed on the basis of theportion 155 is carried out by the microcomputer 144 itself. The dataextraction circuit 145 comprises a frame synchronization detector 163which detects the beginning of each frame on the basis of thesynchronization bits 152 in the frame synchronization bit groups 153.After detection of the beginning of the frame the frame synchronizationdetector 163 supplies a synchronization signal to the microcomputer 144via a signal line 164. Under control of the signals received via thesignal lines 164 and 165 the microcomputer 144 reads in the control dataavailable in the register 160 in an, in principle, customary manner. Itis to be noted that, in principle, the functions of the framesynchronization detector 163 and/or the register 160 and/or the clockextraction circuit 161 can also be performed by the microcomputer 144itself.

In the above described process of reading in the control data from thecontrol files BB and IIDB the clock signal for the register 160 isderived from the synchronization bits 152. However, it is also possibleto derive the clock signal for loading the register 160 from a pictureinformation clock signal which is usually generated in the pictureprocessing unit 141 for the purpose of reading in the coded pictureinformation. This picture information clock signal has a fixedrelationship with the bit group repetition rate in the read-out picturefiles and, consequently, with the bit group repetition rate in thecontrol files BB and IIDB. This is because the control files and picturefiles have been formatted and coded in the same way. Therefore, theclock signal for loading the register 160 can be derived simply from thepicture information clock signal by means of a frequency dividingcircuit.

FIG. 16b shows an example of the data extraction circuit 145, whichemploys a frequency divider 165 for deriving the clock signal for theregister 160, which divider derives the clock signal from the pictureinformation clock signal, which is applied to the frequency divider 165by the signal processing unit 141 via a signal line 166. The clocksignal for loading the register 160 must be synchronized with thebeginning of the frames 154. This can be realized simply by employing aresettable counting circuit for the frequency divider 165, whichcounting circuit is reset each time by a reset signal generated upondetection of the beginning of the frames. The reset signal can be thesignal supplied by the frame synchronization detector 163 via the signalline 164 in response to every detection of the frame synchronization bitgroups 153.

In the case that the information in the control files is arranged inblocks, for example in a manner which is customary with CD-ROM andCD-ROM XA and which will be described hereinafter with reference to FIG.19, the reset signal for the counter can be derived on the basis of theblock synchronization sections (SYNC) situated at the beginning of eachblock (BLCK). However, this requires that the beginning of each frame154 is always situated at a fixed position relative to the blocksynchronization section (SYNC). This can be achieved simply by selectingthe beginning of each frame 154 at the beginning of a block. In the lastdescribed method of synchronizing the clock signal for the register 160no use is made of the frame synchronization bit groups 153 situated atthe beginning of each frame 154. However, in that case it is alsodesirable that the beginning of each frame 154 comprises a number of bitgroups not containing any control data. Indeed, upon detection of thebeginning of each frame the microcomputer calls a read-in program forcontrolling the read-in of the applied control data. However, at thisinstant the microcomputer may be busy performing another control task.Such a control task must be interrupted before the read-in program canbe called. This interruption of an active control task and thesubsequent call for the read-in program requires some time. Arranging anumber of bit groups without any control data at the beginning of eachframe 154 ensures with a high reliability that during read-out of thefirst packet 151 of useful control data in each frame 154 themicrocomputer 144 is ready to read in the control data under control ofthe read-in program. From the above it is evident that thesynchronization bit groups 153 at the beginning of every frame may servea dual purpose, i.e. providing synchronization and producing a waitingtime until the first useful control data is presented.

In the case that the bit groups 153 are used only for realizing thewaiting time the logic values of the bits in these bit groups 153 mayassume an arbitrary value.

If the bit groups 153 are also used for synchronization purposes it isimportant that the bit groups 153 exhibit a bit pattern which does notoccur in the other bit groups of the frame 154. For this purposenumerous different methods are possible, such as for example the use ofnon-identical bit groups in a packet or the insertion of additionalpackets without useful control information between the packets ofcontrol data. The last-mentioned method may be, for example, to insertpackets comprising only bits of the logic value "0" after every tenpackets. When a group of, for example, thirty-two frame synchronizationbit groups 153 comprising only bits of the logic value "1" is used, thiswill guarantee that the pattern formed by the frame synchronization bitgroups 153 does not occur in the other packets of the frame 154.

Picture Storing

FIG. 17 shows an embodiment of the picture storage system 12 in greaterdetail. The scanning unit 1 in FIG. 17 comprises a scanning element 170for scanning the image carrier 3 and for converting the scanned pictureinformation into customary information signals, for example RGB picturesignals, representing the scanned picture. The picture signals at theoutput of the scanning element define the highest attainable resolutionin number of pixels per picture. The information signals supplied by thescanning element 170 are converted into a luminance signal Y and twocolor-difference signals U and V by means of a customary matrix circuit171. A coding circuit 172 converts the signals Y, U and V in a customarymanner into absolutely coded signals (for the lower-resolution pictures)and residually coded pictures (for the higher-resolution pictures) inaccordance with the coding schemes described hereinbefore. The scanningelement 170, the matrix circuit 171 and the coding circuit 172 arecontrolled by means of a customary control circuit 174 on the basis ofcontrol commands applied to the control circuit 174 by the control unit4 via an interface circuit 175. The absolutely and residually codedpicture information generated by the coding circuit 172 is applied tothe control unit 4 via the interface circuit 175. The control unit 4 maycomprise a computer system comprising a display unit 176, a computingand storage unit 177 and a data entry unit 178, for example a keyboard,for data input by the user. In a customary manner the display unit 176and the data entry unit 178 are coupled to the computing and storageunit 177. The computing and storage unit 177 is further coupled to thepicture scanning unit 1 and the recording unit 5 via an interfacecircuit 179 and 180 respectively. The recording unit 5 comprises aformatting and coding unit 181 which converts the information to berecorded, which information is received from the control unit via aninterface circuit 182, into codes which are suitable for recording andwhich are arranged in a format suitable for recording. The data whichhas thus been coded and formatted is applied to a write head 183, whichrecords a corresponding information pattern on the record carrier 184.The recording process is controlled by a control circuit 185 on thebasis of the control commands received from the control unit 4 and, ifapplicable, address information indicating the position of the writehead 183 relative to the record carrier 184.

The storage and control unit 177 is loaded with suitable software toarrange the residually coded picture information supplied by thescanning unit 1 in a customary manner in accordance with theafore-mentioned formatting rules and to compose the picture files IP andOV. Moreover, the computing and storage unit 177 has been loaded withsoftware for inserting in the control file, in a customary manner and inaccordance with the afore-mentioned formatting rules, the preferentialreproduction settings input by an operator together with otherautomatically generated control data, such as for example a list ofaddresses at which the various files have been recorded on the recordcarrier 184.

The computing and storage unit 177 may further have picture processingsoftware enabling the scanned picture information to be processed, forexample for the purpose of error correction, such as for exampleout-of-focus correction and grain removal, or for the purpose of coloradaptation or brightness adaptation of the picture.

The files composed by means of the computing and storage unit 177 areapplied to the recording unit 5 in the desired sequence in order to berecorded.

Very suitable combinations of a record carrier 184 and a recording unit5 have been described in detail inter alia in European PatentApplications no. 88203019.0 to which U.S. Pat. No. 5,001,035corresponds, 90201309.3 to which U.S. patent application Ser. No.08/059,530 corresponds, 8900092.8 to which U.S. Pat. No. 4,901,300corresponds, 8802233.8 to which U.S. Pat. No. 4,979,168 corresponds,8901206.3 to which U.S. Pat. No. 5,060,219 corresponds, 90201094.1 towhich U.S. patent application Ser. No. 07/453,545, now abandoned,corresponds, 90201582.5 to which U.S. patent application Ser. No.07/929,843, now allowed, corresponds, 90200687.3, 90201579.1 to whichU.S. Pat. No. 5,226,027 corresponds, and Dutch Patent Applications no.8902358 to which U.S. patent application Ser. No. 08/041,142 correspondsand 9000327 to which U.S. Pat. No. 5,072,435 corresponds. The recordcarrier described therein is eminently suited for recording informationin accordance with a CD format. A recording device for recording thefiles on such record carrier is shown diagrammatically in FIG. 18. Theshown recording device comprises a formatting circuit 186, whichcomposes the information to be recorded, which has been applied via theinterface circuit 182, in accordance with a formatting scheme, forexample as customary in the so-called CD-ROM or CD-ROM XA system.

By way of illustration this format is shown broadly in FIG. 19. Inaccordance with this format the data is arranged in blocks BLCK of alength corresponding to the length of a subcode frame in the CD signal.Each block BLCK comprises a block synchronizing section SYNC, a headersection HEAD containing an address in the form of an absolute time codecorresponding to the absolute time code in the subcode portion recordedwith the block, and if the CD-ROM XA format is used the block BLCKfurther comprises a subheader section SUBHEAD containing inter alia afile number and a channel number. In addition, each block BLCK comprisesa DATA section containing the information to be recorded. Each blockBLCK may also comprise a section EDC&ECC containing redundantinformation for the purpose of error detection and error corrections.The recording unit 5 shown in FIG. 18 further comprises a CIRC codingcircuit 187 for interleaving the information and for adding parity codesfor the purpose of error detection and error correction (hereinafteralso referred to as error correction codes). The CIRC encoding circuit187 performs the above-mentioned operations upon the formattedinformation supplied by the formatting circuit 186. After theseoperations have been performed the information is applied to an EFMmodulator 188, in which the information is given a form which lendsitself better for recording on the record carrier. Moreover, the EFMmodulator 188 adds subcode information, which includes inter alia anabsolute time code as address information in the so-called subcode Qchannel.

FIG. 20 shows an organization of the record carrier in the case that theinformation has been recorded in the track 20 in accordance with the CDformat described above. Parts corresponding to the organization shown inFIG. 2 bear the same reference numerals.

The recorded information is preceded by a lead-in section LI (alsoreferred to lead-in track), as customary in the recording of CD signals,and is terminated with a customary lead-out section LO (also referred toas lead-out track).

When the information is recorded in CD format it is preferred to includein the control file BB a section recorded in accordance with the CD-Istandard. These sections are the "Disk Label & Directory", referencedDL, and the so-called application programs, referenced AF. This enablesthe recorded picture information to be displayed by means of a standardCD-I system. Preferably, a subfile FPS with the sets of preferentialreproduction settings is also included in the application programsection AF. In addition to the sections DL and AT the control file BBcomprises a subfile IT comprising a section CNTR with control data and asection FPS with the sets of preferential reproduction settings in theformat already described with reference to FIG. 15. Preferably, thesection IT is recorded in a predetermined area on the record carrier ina section of predetermined length. This is in order to simplifyretrieval of the required information by the microcomputer. If thesection IT is not large enough to accommodate all the control data apart of the control data can be recorded in a section ITC after the fileOV. In that case it is preferred to include a pointer in the section ITto specify the starting address of ITC.

For the case that the information has been recorded in CD format FIG. 21shows for the absolutely coded subfile TV such an arrangement of thepicture lines Y01, Y02, . . . , Y16 with absolutely coded luminanceinformation and the picture lines C01, C03, . . . , C15 with absolutelycoded color information, that successive lines do not adjoin each otherin the track direction (also referred to as tangential direction) and ina direction transverse to the track (also referred to as radialdirection).

FIG. 22 shows the positions of the picture lines for the associatedpicture representation. As is shown in FIGS. 21 and 22, a number of oddcoded luminance picture lines (Y01, Y03, . . . , Y15) with codedluminance information are recorded in a section comprising the blocksBLCK #1, #2 and #3, subsequently a number of even coded color picturelines (C01, C05, . . . , C13) with coded color information are recordedin a section comprising the blocks BLCK #4 and #5, then the even codedluminance picture lines (Y02, . . . , Y16) with coded luminanceinformation are recorded in a section comprising the blocks BLCK #5, . .. , #8, and finally the coded even color picture lines (C03, C07, . . ., C15) with coded color information are recorded in a section comprisingthe blocks BLCK #8 and #9. The coded picture lines in the blocks BLCK#1,. . . , BLCK#9 define a contiguous part of the picture representationshown in FIG. 22. A group of sections defining a contiguous part of therepresentation will be referred to hereinafter as a section group. In amanner similar to that described above, section groups define othercontiguous parts of the representation in the subfile TV. The codedpicture lines with picture information for the subfiles TV/4 and TV/16can be arranged in a similar way, as is shown in FIGS. 23 and 24.

This arrangement prevents two or more adjacent picture lines in therepresentation of the read coded picture from being read incorrectly asa result of disc defects. The restoration of representations of picturesin which incorrectly read picture lines adjoin each other is verydifficult to accomplish. This is in contradistinction to the restorationof an incorrectly read picture line situated between two properly readpicture lines in the representation. In the last-mentioned caserestoration is simple by replacing incorrectly read picture lines bypixels derived from adjacent picture lines.

Picture Processing Unit

FIG. 25 shows the picture processing unit 141 in greater detail. Thepicture processing unit 141 comprises a first detection circuit 250 fordetecting the synchronization codes LD and the picture line numbers LNindicating the beginning of each residually coded picture line. A seconddetection circuit 251 serves for detecting the beginning of each subfilein each picture file with a residually coded picture to indicate thebeginning of the section 11DB containing the addresses of a number ofcoded picture lines. It is to be noted that the detection circuits 250and 251 are needed only for processing the residually coded pictures andnot for processing absolutely coded pictures. For the purpose of thesedetections inputs of the first and the second detection circuit 250 and251 are connected to the signal path 142. A decoding circuit 252 fordecoding the residually coded picture information and a control circuit253 for controlling the picture processing operation are connected tothe signal path 142. The signal path 142 and outputs of the decodingcircuit 252 are connected to data inputs of a picture memory 255 via amultiplex circuit 254, to store the read and decoded pictureinformation. Data outputs of the picture memory 255 are connected to theinputs of the decoding circuit 252 and to the inputs of the multiplexcircuit 254.

The control circuit 253 comprises an address generator 256 foraddressing the memory locations in the picture memory 255. The pictureprocessing unit 141 further comprises a second address generator 257 foraddressing the memory locations in order to output the content of thepicture memory to a signal converter 258. The signal converter 258 is ofa customary type which converts the picture information read from thepicture memory 255 into a form suitable for application to the picturedisplay unit 10. The decoding circuit 252 may comprise, for example, aHuffman decoding circuit 261a controlled by the control unit 253 and anadder circuit 259. The Huffman decoding circuit 261a decodes theinformation received via the signal path 142 and subsequently suppliesthis decoded information to one of the inputs of the adder circuit 259.Another input of the adder circuit 259 is connected to the data outputsof the picture memory 255. The result of the adding operation performedby the adder circuit 259 is applied to the multiplex circuit 254.

The control circuit 253 is coupled to the control unit 140 via a controlsignal path 260. The control circuit 253 may comprise, for example, aprogrammable control and computing unit. Such a control and computingunit may comprise, for example, a dedicated hardware unit or amicroprocessor system loaded with suitable control software, by means ofwhich on the basis of control commands received via the control signalpath 260 the address generator 256 and the multiplex circuit 254 arecontrolled in such a way that a selected portion of the pictureinformation applied via the signal path 142 is loaded into the picturememory. The information thus stored in the picture memory 255 is readwith the aid of an address generator 257 and is subsequently applied tothe display unit 10 via the signal converter 258 in order to bedisplayed.

In FIG. 26 the reference numerals 261, 262, 263 denote picturerepresentations of the same picture but with different resolutions. Therepresentation 261 comprises 256 picture lines of 384 pixels each. Therepresentation 262 comprises 512 picture lines of 768 pixels each andthe representation 263 comprises 1024 picture lines of 1536 pixels each.The coded pictures corresponding to the representations 261, 262 and 263are included in consecutive subfiles TV/4, TV and 4TV of a picture fileIP. The capacity of the picture memory 255 shown in FIG. 26 is 512 rowsof 768 memory locations (also called memory elements). If arepresentation should represent the entire coded picture that subfile isselected from the picture file IP, whose number of pixels corresponds tothe capacity of the picture memory, which in the present case is thesubfile defining the representation 262. This selection can be made onthe basis of the setting data, such as picture numbers and resolutionorder (this is the identification of the subfile resolution), which arestored at the beginning of each subfile in, for example, the header HEADand the subheader SUBHEAD of the blocks BLCK. For each subfile this datais read in by the control circuit 253 in response to a signal suppliedby a block synchronization detector 262a upon detection of the beginningof each block BLCK.

In the case that a representation of an absolutely coded picture is tobe reproduced, upon detection of the beginning of the subfile to beselected, the control circuit sets the multiplex circuit 254 to a statein which the signal path 142 is connected to the data inputs of thepicture memory 255. Moreover, the address generator 256 is set to astate in which the memory locations are addressed in synchronism withthe reception of the successive pixel information, in such a way thatthe information for the picture lines 11, . . . , 1512 is stored in therespective rows r1, . . . , r512 of the memory 255. The pictureinformation thus loaded into the memory 255 is read out and is convertedinto a form suitable for the display unit 10 by means of the signalconverter 258. The read-out sequence is determined by the sequence inwhich the address generator 257 generates the successive addresses.During normal reproduction this sequence is such that the memory is readin a row-by-row fashion, starting with the row r1 and starting withcolumn c1 within a row. This is possible both in accordance with theinterlaced-scan principle and the progressive-scan principle. In thecase of read-out according to the interlaced-scan principle all the oddrows of the picture memory 255 are read first and subsequently all theeven rows of the picture memory 255 are read. In the case of read-out inaccordance with the progressive-scan principle all the rows are read insequence.

A very attractive alternative for the method of storing the pictureinformation in the picture memory 255 is that in which the picturememory 255 is first filled with picture information from a picture filedefining a lower-resolution representation of a picture and subsequentlythe content of the memory is overwritten with a coded picture defining ahigher-resolution representation of the same picture. In the aboveexample this is possible in that during read-out of each coded pixelfrom the subfile TV/4 each of a group of 2×2 memory elements is eachtime filled with the signal value defined by this coded pixel. Thismethod is known as the "spatial replica" method. A better picturequality is obtained by filling only one of the memory elements of the2×2 matrix with the signal value defined by a read-out pixel, and byderiving the other pixels of the 2×2 matrix from adjacent pixels bymeans of known interpolation techniques. This method is known as the"spatial interpolation" method. After detection of the next subfile (inthe present case TV) the content of the picture memory is each timeoverwritten with the picture information of this subfile in the methodsdescribed above. The amount of information in the subfile TV/4 is only aquarter of that in the subfile TV. This results in a substantialreduction of the time after which a first provisional picture isdisplayed on the display unit. After read-out of the picture file TV/4this low-resolution picture is overwritten with a representation of thesame picture having the desired resolution. As the picture files withcoded pictures of successive resolutions succeed one another directly notime is lost in searching for the subfile TV after read-out of thesubfile TV/4.

In the case that a picture is to be rotated the address generator 256 isset to a state in which the sequence of addressing the memory locationsis adapted in accordance with the desired rotation angle. FIGS. 27b, 27cand 27d illustrate how the picture information is stored in the memoryfor a rotation through an angle of 270, 180 and 90 degrees respectively.For the sake of clarity these Figures only show the positions of theinformation of the first two picture lines 11 and 12 of the picture.

In the case that a representation of a small picture is to be displayedwithin the outline of a full-scan representation of another picture or,if desired, the same picture (PIP function), this can be achieved simplyby filling the desired location of the picture memory 255 with thelow-resolution picture of the subfile TV/4 without magnification. Whenthe picture memory 255 is filled the address generator 256 is then setto a state in which the information for memory locations is addressed inwhich the small picture is to be stored. To illustrate this these memorylocations are represented as a frame 264 in FIG. 26. During the pictureprocessing described above the presence of the low-resolution picture inthe subfile TV/4 again has the advantage that the picture informationrequired to perform this function is directly available in the picturefile IP, so that additional processing is not necessary.

When an enlarged representation of a part of the absolutely codedpicture is to be displayed the information of a part of the picture, forexample the part corresponding to a frame 265, is selected. Theinformation of each pixel of the selected part is loaded into everymemory location of a group of 2×2 memory locations, so that a magnifiedfull-scan representation of low resolution is displayed on the displayunit. Instead of repeating each pixel 2×2 times in the memory the memorymay be filled in accordance with the spatial-interpolation principlementioned in the foregoing.

In order to magnify the residually coded pictures the above step isperformed first. Subsequently, the part represented by the frame 266 isselected in the subfile 4TV. The part in the frame 266 corresponds tothe part within the frame 265 in the representation 262. The controlcircuit 253 sets the multiplex circuit 254 to a state in which theoutput of the residual decoding circuit 252 is connected to the datainputs of the memory 255. The address generator 256 is set to a state inwhich it addresses the picture memory 255 in synchronism with thereceived coded pixels in the sequence in which the residually codedpicture information from the subfile 4TV becomes available. The pictureinformation in the addressed memory locations is applied to the decodingcircuit 252 and by means of the adder circuit 259 it is added to theresidual value, after which the information thus adapted is loaded intothe addressed memory location. The part of the picture informationrecorded on the record carrier corresponding to the frame 266 ispreferably read on the basis of the information in the control fileIIDB. The information in the section IIDB is read in by the controlcircuit 253 in response to a signal from the detector 250. Subsequently,from this information, the control circuit 253 selects the address ofthat coded picture line which is situated shortly before the first codedpicture line corresponding to the picture line in the frame 266. Afterthis, the control circuit supplies a command to the control unit 140 viathe control signal path 260, which control unit in response to thiscommand initiates a search process in which the part with the selectedcoded picture line is located. When this part is found the read-out ofthe picture information is started and the adaptation of the content ofthe memory 255 is started as soon as the part of the first coded pictureline which corresponds to the part of the picture within the frame 266is reached. The detection of this coded picture line is effected on thebasis of the line numbers which together with the line synchronizationcodes LD have been inserted at the beginning of each coded picture line.The control circuit reads in these line numbers LN in response to asignal from the detector circuit 251. The storage of the addressinformation at the beginning of the subfile 4TV enables a rapid accessto the desired information to be obtained. The detection of the read-outof the desired residually coded picture lines is simplified by thepresence of the line synchronization codes and line numbers in thesubfile 4TV.

Record Courier Read Out

FIG. 28 shows an embodiment of the read unit 6 by means of which it ispossible to read out the coded picture information recorded on therecord carrier by means of the recording unit shown in FIG. 18. Theshown read unit 6 comprises a customary read head 280 which reads theinformation patterns on the record carrier 184 by scanning the track 20and converts the resulting information into corresponding signals. Theread unit further comprises a customary positioning unit 284 for movingthe read head 280 in a direction transverse to the tracks to a portionof the track 20 specified by a selected address. The movement of theread head 283 is controlled by a control unit 285. The signals convertedby the read head 280 are decoded by an EFM decoding circuit 281 and aresubsequently applied to a CIRC decoding circuit 282. The CIRC decodingcircuit 282 is of a customary type, which restores the originalstructure of the information which has been interleaved prior torecording and which detects and, if possible, corrects incorrectly readcodes. Upon detection of incorrigible errors the CIRC decoding unitsupplies a new error flag signal. The information which has beenrestored and corrected by the CIRC decoding circuit 282 is applied to adeformatting circuit 283 which removes the additional information addedby the formatting circuit 186 prior to recording. The EFM demodulatingcircuit 281, the CIRC decoding circuit 282, and the deformatting circuit283 are controlled in a customary manner by the control unit 285. Theinformation supplied by the deformatting circuit 283 is applied via aninterface circuit 286. The deformatting circuit may comprise an errorcorrection circuit by means of which errors which cannot be corrected bythe CIRC decoding circuit can be detected and corrected. This iseffected by means of redundant information EDC & ECC added by theformatting circuit 166. The error correction circuit, which iscomparatively complex and therefore comparatively expensive, is notnecessary. This is because the effects of erroneously read codes in theabsolutely coded picture information can be masked simply by replacingthe incorrectly read coded pixels and/or a complete coded picture lineby picture information derived from one or more adjacent coded pixels oradjacent coded picture lines. Such a correction can be effected simplyby means of the signal processing unit 141 shown in FIG. 25, byprogramming the control circuit 253 so as to be responsive to the errorflag signal supplied by the CIRC decoding circuit 282 to control theaddress generator 256 in such a way that the information of an adjacentpixel is read and, at the same time, the multiplex circuit 254 is set toa state in which the data outputs of the picture memory 255 areconnected to the data inputs. Subsequently, the address generator isreset to its previous state and instead of the incorrectly read codedpixel the information read from the picture memory 255 is stored at theaddressed memory location.

In the case that a residually coded picture is read the value in thememory 255 is not adapted upon detection of an incorrectly read residualvalue but remains unchanged. This can be achieved, for example, bycausing the control circuit to generate a signal which inhibits writinginto the memory 255 when the erroneous residual value is applied.

The capacity of the picture memory 255 is large, so that the cost priceof such a memory is comparatively high. The memory capacity may bereduced by arranging between the multiplexer 254 and the picture memory255 a sample rate converter 290 of a customary type, which reducers thenumber of pixels per line from 786 to 512.

FIG. 31 shows an example of the sample rate converter 290. The presentexample comprises a series arrangement of an upsampling andinterpolation circuit 310 and a low-pass filter 311, and a downsamplingand decimating circuit 312.

The use of the sample rate converter 290 enables a memory of 512 by 512memory locations to be employed. Since for practical reasons the numberof rows and the number of columns of memory locations in a memory arepreferably powers of two, this yields a memory of particularlysatisfactory dimensions. Moreover, as a result of the reduction of thenumber of memory locations to 512 per row the required memory read-outfrequency is reduced, so that less stringent requirements have to beimposed on the read-out speed of the memories used.

The usually employed picture tubes have a maximum resolutioncorresponding to approximately 5 MHz, which corresponds to approximately500 pixels per line, so that the reduction of the number of memorylocations per row has no visible effects on the reproduced picture.

The use of the sample rate converter is also advantageous whenportrait-format representations of pictures are to be displayed on adisplay screen, which will be explained hereinafter with reference toFIGS. 30a, 30b, 30c and 30d.

In FIG. 30a the reference numeral 300 refers to the dimensions of apicture in accordance with the PAL TV standard. Such a picture inaccordance with the PAL TV standard comprises 575 useful picture lines.During reproduction of the information in the picture memory of 512×512memory elements 512 of these 575 useful picture lines are utilized. Thismeans that a representation 301 of the coded picture in the picturememory fits completely within aspect ratio of the frame 300 as definedby the PAL TV standard, only a small part of the available displayscreen area being left unused.

In FIG. 30b the reference numeral 320 denotes a frame having thedimensions of a picture in accordance with the NTSC TV standard. Such apicture in conformity with the NTSC TV standard comprises 431 usefullines. This means that only a limited part of a representation 303 ofthe coded picture present in the picture memory 255 falls outside theoutline of a picture in accordance with the NTSC standard.

FIGS. 30a and 30b concern landscape-format reproductions ofrepresentations of coded pictures. However, if portrait-formatrepresentations of coded pictures are required the problem arises thatthe height of the picture corresponds to 768 pixels, the number ofuseful picture lines being 575 in accordance with the PAL TV standardand 485 in accordance with the NTSC TV standard. When a picture memoryof 512 rows of memory locations is employed without the use of thesample rate converter 290 this would mean that a coded picture line doesnot fit in one memory column. However, by the use of the sample rateconverter 290 it is achieved that the coded picture lines of 768 codedpixels are converted into coded picture lines of 512 coded pixels, sothat a coded picture line can be accommodated in one memory column. Thismeans that during reproduction the height of the representation of thepicture stored in the memory 255 substantially corresponds to the heightof the picture frames defined in the PAL and NTSC TV standards.

In order to ensure that the ratio between the length and width of therepresentation of the coded picture stored in the picture memory 255corresponds to the original ratio it is required to fill only 256 of the512 columns of the picture memory with picture information. This ispossible, for example, by storing only the even or only the odd codedpicture lines in the memory 255. However, other methods utilizinginterpolation techniques may also be used.

The method of reducing the number of columns in the picture memoryemploying interpolation techniques yields a picture representation ofsatisfactory quality. This is in contradistinction to the method inwhich only a part of the coded picture lines is stored in the columns ofthe picture memory.

A drawback of interpolation techniques is that they are comparativelyintricate and time-consuming, so that they are less suited for use inthe simplified picture retrieval and display system. A method whichyields pictures of satisfactory quality in a simple manner will bedescribed hereinafter for the case that the picture memory comprises512×512 memory locations. This method uses the subfile TV/4 with 384×256coded pixels, instead of the subfile TV with 768×512 coded pixels, forloading the picture memory.

The use of a sample rate converter 20, by means of which the number ofpixels per read coded picture line can be reduced and increased, enablesthe number of pixels per read coded picture line of the subfile TV/4 tobe increased from 384 to 512. The 256 available adapted picture lines of512 coded pixels each are loaded into the memory 255. Thus, 256 columnsof 512 memory locations each are filled with picture information.Reading out this information yields an undistorted portrait-formatrepresentation, whose height substantially corresponds to the height ofthe display screen of a PAL or NTSC TV system, and whose quality issubstantially better than that of a portrait-format representationobtained on the basis of a coded picture of 768×512 coded pixels whosewidth is adapted by using only half (256) the available number of 512coded picture lines.

By way of illustration FIG. 30c shows a portrait-format representation304 of the stored coded picture (of 256×512 coded pixels) thus obtainedwithin the frame 300 defined by the PAL TV standard. The entirerepresentation falls within the frame defined by the PAL standard. FIG.30d by way of illustration shows a portrait-format representation of thecoded picture thus stored. The representation falls largely within theframe 302 defined by the NTSC TV standard.

As will be apparent from the foregoing the use of a sample rateconverter 290 enables the use of a picture memory having equal numbersof rows and columns and corresponding substantially to the number ofuseful picture lines in accordance with the NTSC or PAL standard. Thismeans that both in the case of portrait-format and landscape-formatrepresentations of coded pictures the height of the representationsubstantially corresponds to the number of useful picture lines, so thatthe display screen will be filled correctly for representations of bothtypes.

I claim:
 1. A picture retrieval combination for locating and retrieving selected coded picture lines stored on a record carrier, said combination comprising:a) a record carrier on which a multiplicity of coded picture lines and a plurality of addresses are recorded in a track, said coded picture lines representing a coded picture composed of a sequence of consecutive coded picture lines, each respective one of said consecutive coded picture lines having a line synchronization code and a respective line number recorded at the beginning of that one coded picture line, each line synchronization code marking the beginning of the respective coded picture line and each line number specifying the sequence number of the respective coded line in said sequence; and said addresses being a plurality of addresses each specifying the location on said track of a respective given picture line; and b) a reading apparatus comprising:a read head for reading said coded picture lines and said addresses by scanning said track; line selecting means for selecting one of said respective given picture lines; address selecting means, responsive to said line selecting means, for selecting that one of said plurality of addresses which corresponds to said one of said respective given picture lines; moving means, responsive to said address selecting means, for causing relative movement of said read head with respect to said track, such that said read head scans the location on said track corresponding to said one of said addresses; and means coupled to said read head for detecting the beginning of said one of said respective given picture lines on the basis of its respective line number and line synchronization code.
 2. A combination as claimed in claim 1, characterized in that said location corresponding to said one of said addresses is a location before the beginning of said one of said respective given picture lines.
 3. A combination as claimed in claim 1, characterized in that the number of said plurality of addresses is less than the number of said multiplicity of coded picture lines.
 4. A combination as claimed in claim 3, characterized in that said location corresponding to said one of said addresses is a location before the beginning of said one of said respective given picture lines.
 5. A combination as claimed in claim 4, characterized in that said moving means has a search accuracy corresponding to a given distance along said track, and consecutive locations specified by said plurality of addresses are separated by a distance substantially corresponding to said given distance.
 6. A combination as claimed in claim 5, wherein said record carrier is a disc having a central axis, said read device includes means for rotating said disc about said axis, said moving means moves said read head substantially radially with respect to said axis, and said at least one track is a spiral track,characterized in that said given distance is substantially half the length of a turn of said spiral track.
 7. A combination as claimed in claim 1, characterized in that said coded picture lines are encoded according to a variable-length code.
 8. A combination as claimed in claim 7, characterized in that said location corresponding to said one of said addresses is a location before the beginning of said one of said respective given picture lines.
 9. A combination as claimed in claim 7, characterized in that the number of said plurality of addresses is less than the number of said multiplicity of coded picture lines.
 10. A combination as claimed in claim 9, characterized in that said location corresponding to said one of said addresses is a location before the beginning of said one of said respective given picture lines.
 11. A combination as claimed in claim 10, characterized in that said moving means has a search accuracy corresponding to a given distance along said track, and consecutive locations specified by said plurality of addresses are separated by a distance substantially corresponding to said given distance.
 12. A combination as claimed in claim 11, wherein said record carrier is a disc having a central axis, said read device includes means for rotating said disc about said axis, said moving means moves said read head substantially radially with respect to said axis, and said at least one track is a spiral track,characterized in that said given distance is substantially half the length of a turn of said spiral track.
 13. A record carrier for pictures stored as a multiplicity of coded picture lines, and arranged to permit rapid retrieval of a selected coded picture line, characterized in that:said coded picture lines and a plurality of addresses are recorded in a track, said coded picture lines represent a coded picture composed of a sequence of consecutive coded picture lines, each respective one of said consecutive coded picture lines having a line synchronization code and a respective line number recorded at the beginning of that one coded picture line, each line synchronization code marking the beginning of the respective coded picture line and each line number specifying the sequence number of the respective coded line in said sequence, and each of said addresses specifies the location on said track of a respective given picture line.
 14. A record carrier as claimed in claim 13, characterized in that the number of said plurality of addresses is less than the number of said multiplicity of coded picture lines.
 15. A record carrier as claimed in claim 14, characterized in that said coded picture lines are encoded according to a variable-length code.
 16. A picture retrieval apparatus for reading selected coded picture lines stored on a record carrier which has a multiplicity of coded picture lines and a plurality of addresses recorded in a track,each respective one of said consecutive coded picture lines having a line synchronization code and a respective line number recorded at the beginning of that one coded picture line, each line synchronization code marking the beginning of the respective coded picture line and each line number specifying the sequence number of the respective coded line in said sequence, and the number of the plurality of addresses being less than the number of coded picture lines, each of said addresses specifying the location on the track of a respective given picture line, characterized in that the apparatus comprises:a read head for reading said coded picture lines and said addresses by scanning said track, line selecting means for selecting a first coded picture line, address selecting means, responsive to said line selecting means, for selecting that one of said plurality of addresses which corresponds to said first coded picture line, moving means, responsive to said address selecting means, for causing relative movement of said read head with respect to said track, such that said read head scans the location on said track corresponding to said one of said addresses, and means coupled to said read head for detecting the beginning of said first coded picture line on the basis of its respective line number and line synchronization code.
 17. An apparatus as claimed in claim 16, for reading said lines on a record carrier formed as a disc having a disc axis, consecutive locations specified by said plurality of addresses being separated by a distance substantially corresponding to a given distance,wherein said apparatus further comprises means for rotating the disc about the disc axis, and the moving means is arranged for moving the head radially with respect to the disc axis, characterized in that said moving means has a search accuracy corresponding to said given distance along said track.
 18. A combination as claimed in claim 1, characterized in that said plurality of addresses is stored separately from the corresponding multiplicity of coded picture lines.
 19. A picture retrieval combination for locating and retrieving selected coded picture elements for a picture stored as compressed data on a record carrier, said combination comprising:a) a record carrier on which a multiplicity of coded picture elements and a separately stored plurality of addresses are recorded in a track, said coded picture elements being a sequence of elements representing a coded picture composed of a sequence of picture lines, each respective one of said consecutive coded picture elements having an element synchronization code and a respective element number recorded at the beginning of that one coded picture element, each element synchronization code marking the beginning of the respective coded picture element and each element number specifying the sequence number of the respective coded element in said sequence of elements; and said addresses being a plurality of addresses each specifying the location on said track of a respective given picture element; and b) a reading apparatus comprising:a read head for reading said coded picture elements and said addresses by scanning said track; element selecting means for selecting one of said respective given picture elements; address selecting means, responsive to said element selecting means, for selecting that one of said plurality of addresses which corresponds to said one of said respective given picture elements; moving means, responsive to said address selecting means, for causing relative movement of said read head with respect to said track, such that said read head scans the location on said track corresponding to said one of said addresses; and means coupled to said read head for detecting the beginning of said one of said respective given picture elements on the basis of its respective element number and element synchronization code.
 20. A combination as claimed in claim 19, characterized in that said coded picture elements have a variable length.
 21. A combination as claimed in claim 20, characterized in that said coded picture elements are picture lines.
 22. A combination as claimed in claim 19, characterized in that a number of addresses less that the total number of picture elements is stored. 